JPS60241323A - Output protective circuit - Google Patents

Abstract

PURPOSE:To protect an output transistor (TR) by detecting a substrate current of a large-output driver IC which is generated when the output TR is overloaded. CONSTITUTION:When the output TR is overloaded, the substrate current is generated in a P<-> substrate by positive holes 8 and 13. This substrate current is detected by a P<+> diffusion 4. The detected substrate current is converted to a voltage by a resistance 2 and is converted to an output control signal by a TR3 and is inputted to an output control circuit which turns off gates 6 and 11 of the output TR. The value of the resistance 2 and the threshold voltage of the TR3 are set to proper values to turn off the output TR at the overload time, thus protecting the output TR.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a large output driver integrated circuit C (hereinafter referred to as IC)
related to output protection circuits.

A high-output driver C that drives high voltage and large current is equipped with an output protection circuit because its output transistor will be destroyed due to an output short circuit, excessive consumption, etc., and this will have a large effect on external equipment.

[Prior art]

Typical examples of conventional output protection circuits are shown in FIGS. 1 and 2.

In FIG. 1, the output of the transistor is connected through a resistor 1 to an output terminal OUT. When resistor IK current flows, a voltage is generated in the detection device, but if a current exceeding the standard flows, the output control device is activated and the output is turned off! OF
II' L, stop the current and avoid destroying the output transistor.

This method cannot prevent latch-up inside the XC, which is a phenomenon that occurs with CMOB'LC19, and in the case of the M08 transistor, it is difficult to insert a resistor on the source side because of the reduction in performance due to the hack gate effect. In addition, in the case of the device C that drives a large current, the overcurrent detection resistor in the output stage becomes a load, which has an adverse effect on the characteristics and reliability of the IC, such as a reduction in output capability and heat generated by the overcurrent detection resistor.

Furthermore, it is necessary to attach a detection resistor to all output stages, and in a large output driver IC having multiple outputs, the detection resistor alone occupies a large area.

In FIG. 2, a temperature sensor inside the IC senses heat generation due to excessive current, and when the temperature reaches a certain level, the output control device operates to protect the output transistor by setting it to 0FFL.

This method detects temperature, and current continues to flow until the temperature of the IC rises. Therefore, until the temperature sensor works, a large burden is placed on the output transistor.
There was a drawback that the output transistor would be destroyed before the temperature of the IC rose.

Furthermore, since it relies on temperature control, it is easily affected by the mounting method of engineering C and the ambient temperature, making it unstable as a control system.

〔the purpose〕

The present invention eliminates such drawbacks, and its purpose is to provide an output protection circuit for avoiding output transistor destruction caused by overloading, output terminal short-circuiting, etc. in high-power driver ICs having high voltage, large current, and drive elements. The purpose is to provide it in a small area.

〔overview〕

The output protection circuit of the present invention is characterized in that in a large output driver C, the output transistor is controlled and protected by detecting the substrate current of the IC that occurs when the output transistor is overloaded.

〔Example〕

The present invention will be described in detail below based on Examples.

FIG. 8 explains the basic principle of the present invention. FIG. 4 shows a specific circuit from substrate current detection to the output control system.

In Figure 8, when the internal electric field of the MOS (MOS) range meter increases, the carrier flowing through the channel becomes the drain (7).
It is accelerated in the high electric field region near '(11), promoting impact ionization, and weak avalanche multiplication occurs. For this reason, electron-hole pairs are generated. Taking the D substrate as an example, in PMOEl, electron [12] flows to the NWIDI, I, side, and in NMO8, the hole (8) flows to the substrate side, and the substrate current increases. arise.

Inside NWEiLL (7) P M OS drain (11
) The potential of the NWEiLL is lowered by the electrons generated in the vicinity, turning on the vertical PNP parasitic transistor (14), and holes (13) enter the P substrate.

When the output transistor is overloaded, holes (8X
13) Substrate current is generated in the lure substrate by K.

The electron-hole production rate in the drain/nearby region is a function of the drain field and drain current, and the substrate current increases when the transistor is overloaded.

Utilizing this, the substrate current that occurs when the output transistor is overloaded is detected by the P diffusion (4), and by passing this through the resistor (2), the substrate current is extracted as a voltage and signal, and the control signal for the output system is shall be.

In FIG. 4, the current detected by the substrate current detection (FIG. 8 4) is converted into voltage by the resistor G2) 4C,
Pch) becomes the output control signal by range meta (8) and turns off the output transistor gates (6) (13)
is input to the output control circuit.

By setting the value of the resistor (2) and the threshold voltage of the transistor (8) to appropriate values, the output transistor can be set to 0FIF during overload, and the output transistor can be protected.

The above embodiment is an example in which the substrate current is detected by making contact with a small substrate through dense diffusion, but the transistor performance decreases due to the substrate current and the threshold voltage C
Detection is also possible by utilizing the property of an increase in Vth (hereinafter referred to as vth).

A specific circuit example will be explained below.

FIG. 5, FIG. 7, and FIG. 8 are specific circuit diagrams according to the present invention. FIG. 6 is a diagram in which the circuit shown in FIG. 5 corresponds to the engineering C layout.

In FIG. 6, the substrate current detection transistor 06) is the same as the output transistor -WI! ! This is an example where it is installed in LTJ (Canada). The transistor (19) has a slightly larger capacity than the transistor (17), and its normal output is in the write L1 state. The substrate current generated by the output transistor reduces the capability of transistor (16) and shifts the gate potentials of transistors α7] and (19) lower. This is K jD) The capability of the range meta (17) is greater than that of the transistor (19), so the output is 'H'
K is pulled. This change is output as an output control signal.

Therefore, in order to eliminate the effect of substrate current, the transistor (17) is connected to the output transistor and another wxr, r, (2p
formed within.

The above is the detection of substrate current in NWFiLL, but P-
Regarding the substrate current in the substrate, the transistor 0FDp
Apply appropriate isolation to (19) K and C.
) can be detected with Rangemetal 08).

In FIG. 7, the transistor (22) is for substrate current detection, and the transistor (2) is a feedback transistor for applying a reference voltage (in this case, vth of transistor 22) to point A.

The voltage across the resistor (24) is always maintained at vth of the transistor (22) by the transistor (23).
The current t (26) flowing through the resistors (24) and (25) is as follows.

・vth 1=R1 Therefore, the voltage VB across the resistor (25) is as follows.

y B =-LygIL 1 Here, if vth of the transistor (22) changes due to the substrate current, VB also changes.

This is output as an output control signal.

In FIG. 8, transistors (27) to (30) constitute a bridge circuit. transistor (27),
(28) or (29) and (30) are transistors of the same size and are normally in a balanced state. If the characteristics of this transistor change due to the substrate current,
The equilibrium state is disrupted and a potential difference occurs between C and D. This is passed through a differential amplifier (31) and output as an output control signal.

This method can create an equilibrium state of the bridge regardless of the IC manufacturing conditions.

In FIG. 9, the output signal obtained by the substrate current is controlled by performing an A N D (32) with each bit signal.

〔effect〕

The present invention protects the output of a high-output driver C and avoids damage to the output transistor caused by short-circuiting of the output terminals.

This eliminates the influence of destruction of the engineering C on external equipment, leading to improved reliability of the engineering C itself as well as the reliability of the system in which the engineering C is incorporated.

In addition, there is no need to detect the substrate potential used as a sensor for the output protection circuit for each output, and in multi-output drivers, there is almost no increase in chip area due to the addition of an output protection circuit, so chip costs can be kept low. It has excellent effects such as

Furthermore, in MOEI C, by detecting the substrate current caused by the transistor and controlling the power supply,
With 8IC, it is also possible to avoid destruction of the IC due to latch-up inside the IC, which is said to be fatal.

Although the present invention uses a P-substrate as an example, it goes without saying that the theory can be developed in exactly the same way by changing the polarity of a single substrate.

Furthermore, according to the output control principle of the present invention, P on the N-substrate
It is also possible to control the output by detecting the substrate current in 1iWKLI+ on the WELL or P− substrate.

[Brief explanation of drawings]

FIG. 1 shows a conventional output protection circuit in which an excessive current flowing through a single output transistor is detected by a resistor 1, and the output is controlled and protected. FIG. 2 is another example of a conventional output protection circuit, which detects and protects IC heat generation due to excessive current. FIG. 8 is a sectional view of the IC of the output protection circuit according to the present invention, which detects changes in transistor performance due to flow. FIG. 5 shows the circuit shown in FIG. 6 in correspondence with the IC layout. FIG. 7 shows an example of an output protection circuit according to the present invention, which detects changes in vth of a transistor due to substrate current. FIG. 8 is an example of an output protection circuit using a bridge. FIG. 9 is a specific example of a circuit for output control. Applicant Suwa Seikosha Co., Ltd. Agent Patent Attorney Mogami 1617 Figure 5 819 Figure 6 728 Figure 8

Claims (1)

[Claims] An output protection circuit for an integrated circuit having a high-voltage, large-current drive element, characterized in that a protection control signal is obtained from a substrate current of the integrated circuit.